This application relates to rotary-faced valves for the control of flow of pressurized fluid, and more particularly, to a valve that has a pressure balance across the faces of a rotary disk that controls the flow of fluid within the valve.
Rotary disk valves are known in the prior art. One class of device is described by Cyphelly in U.S. Pat. No. 3,768,516. Operation of the described device relies on the use of a rotary disk valve disposed between a pump and a hydraulically-actuated piston. The valve disk is provided with grooves to connect either side of the pistons selectively to pump and sump in order to extend and retract the piston. Cyphelly is directed to a rotary control valve in which the gap width between the fixed and movable valve parts that control the flow of pressurized hydraulic fluid is maintained by hydrostatic pressure of the controlled fluid. The fluid pressure in the gap is maintained by a pressure relief conduit and a throttling device coupled to the conduit for maintaining a pressure differential between portions of the conduit that are separated by the throttling device when the fluid flows through the conduit. Such construction, it is believed, gives rise to large forces acting in a direction to urge the fluid control members apart. Another problem of the device described is that forces exerted on the fluid sealing elements within the controlled chambers are high placing severe requirements on the sealing elements to prevent leakage between the movable parts of the valve.
Another such valve is described by Sharp in U.S. Pat. No. 2,990,853. Sharp describes a rotary valve having a valve plate which is both slideably and rotatably supported in a chamber adjacent the inlet and exhaust ports. Sharp attempts to balance the pressure on both sides of the valve plate by admitting a small amount of high-pressure inlet fluid to leak around the valve plate. The amount of fluid is sufficient to control the turning resistance of the valve plate. The pressure of the inlet fluid on the rotary member is thus counter-balanced by a fluid pressure force on an opposite side of the rotary member. Although Sharp describes pressure balance on both sides of the valve rotary member, the device includes slideable as well as rotary motion of the member, and the pressure balance is accomplished by pressure leakage around the valve plate. Such leakage, it is believed, causes the unwanted admission of pressurized fluids into the conduits that communicate with the devices being controlled. Thus, corrections must be made to compensate for the leakage-induced flow to the controlled device.